Signaling



March 3, 1931. R A: WEAGANT 1,794,878

GRID PTENT/AL SMA/AL GRID 4 @am I f ,f' y Roy A. WEAGANT ATTORNEY March 3, 1931. R, A, WEAGANT 1,794.878

SIGNALING Filed Aug; 30, 1928 2 Sheets-Sheet 2 INVENTO ROY A. WEAGAN ATTORNEY PatentecllMar. 3,. 1931 Y f nox `Ai.Exei'vniiit WEAGANT, or noUGnAsToii, NEWY'RK, AssI'GNoR. To ifm`inio'z1oiz.-`

PORATION OF AMERICA, `A COREQlR-.A'JJIONOF` DELAWARE .SGNALING Application filed August 30, 1.928."7 Seria1"No. 303,095.

This invention relates tonhigh vfrequency signaling -andjparticularly to methods and" arrangements for securing:discrimination bejy though the invention is applicableto'signalf` 'ing with high frequency vrcurrents overnwires,

it is particularly applicable'to wireless signali-ng and will be herein described particu-.

-larlyin relation to? the latter. e

At present two fundamental `meth`ods of i discrimination are Yknown yand -widely used in radio signaling.. The first depend-s on .the

' utilization ofV receivingdevices more sensi- -tive lto currents'f'ofthe desired frequency than to currents' of anotherfrequency. By f this' means wev eliminate signals from othervsta- A tions of different frequencyand that portion ofthe statica or atmosphericy interference rection.A

' Although these fundamental methodsy of .discrimination provide frequency and geographical selectivity, no method Vhas `heretoe fore been linownyandxas far as I am aware, .has even been suggested forY discriminating between oscillations of exactly the lsame freV` quency .coming vfrom thesame direction. 1

The principal object .of the invention is to Y provide a method and apparatus adapted to permit this distinction to be made.

In accordance with thev invention this result is obtained by discriminating by means of differences yexisting between the phase ofthe oscillations. `Phase.'discrimination.is only possible between waves ofV `identical frequency,and this excludes modulated waves, for the modulation :results in vside band lfrequencies 'which'diifer from the carrier, andl which will therefore beat witha locally supplied `carrier regardless of phase. My inven- .tion is .more especially. adapted to long wave i phase/without altering frequency orfamplif ties of the method andv of structures employwork, and is.A limited to phase discrimination 1 between code or other on vand ofi' signals transmitted on vcontinuous waves or pure carriers of identical frequency By this method of .25.5.

discrimination in conjunction 'with v one Y ;orj

both of 4the usual 'methods of differentiation heretofore -mentioned one or more benefits maybe secured among which the yfollow-ing arementioned by 'way'of example? v (l) Currents due to atmospheric disturb` .ancehaving the same frequency as the-signal v may be.exc luded,the extent of .the exclusion f beingv substantially similarto that effected nal direction. n

by directional reception in respect to; static coming from directionsdiferent than the'sigf p, rlwo or more'oiscillationsmaybe-trans!' mittedfrom the. sameplace'on the same wave length v"and receivedwithout interference, either onthe same or'dierent antennae. j i .(13) The -.signaling, :instead fofnbeing,` ef-v fected A:by f detuning or changing the ampli#Y tude, 'may-be accomplished by' changing .the

tu.d`e.n. l Y Y i (4) The system is highly4 secretivey as-'no ordinaryftuned receiver can distinguish 'be-` tween the two signals.

.Further objects, advantagesand capabilii' y ing the method will -appearfrom thefoljlewing description` and drawingsv offseve'ralvemv4bodiments illustrating the invention.` a

i 'The novel featureswhich believe tofbe characteristic of my -invention l are Aparticularly set forth in the appended claims, the invention itself, however, both as" to its con. 'struction and mode of l operation,y vrtogether with further obj ects andv advantages Vthereof will best be understood by-"referencetothe following description Y taken Y, in 'connection with the accompanying vdrawings inwhich: Y Figure l is ardiagr'ammatic representation `'of a transmitting system adapted ltofbexutiv lized in 'conjunction with the method and l j' Figure Qris a similar-representation ofv are Y ceiviiig station adaptedl tok cooperate v@there With.` Figure 3 i-s' a curveshowing the effect of the certain electromagnetic forces on the receiving system. l

Figures 4 and 5 illustrate the manner in which the signal and auxiliary electromotive forces are combined. Figure 6 is a .curve showing the characteristics of the system with respect yto static elimination.

In securing discrimination between desired signalsV and lother interfering signals or Vtransient or atmospheric influences of the same frequency, in accordance with my invention, it is necessary to provide sources of oscillatory energy at the ti'ansmitterand receiver which are of very constant frequency.V In general, the frequency of each of these 4"controlling oscillators will be the radio frequency which is used for transmission. For satisfactory operation,v the variations of frequency or the shifting of the' phase Vrelations between the .controlling loscillators should only occur at such a slow rate that the variations can be conveniently taken care of by manual or automatic adjustment to maintain synchronism'.

Y Vhenever ordinary high yfrequency systems refer to the use at the transmitter and receiver of circuits timed to the same frequency oroscillators of the same frequency. it is always understood' that adifference of or even considerably more is accurate adjustment. rAs far as I am aware no high frequency signaling systems `have even i been suggested which require such constancy may energize separate aerials. oscillations is dephased relatively to those of that the phase of thel oscillations is material as a difference of 1/2 or even -115 lof11% would be a large number of cycles; To distinguish from this ordinary usage, the constancy of the oscillatorsheretofore specified asnecessary to the operation will be designated by the term in substantially definite phase relatioiis. This accuracy of frequency regulation may be reached with exceedingly carefullyl constructed vacuum tube oscillation generators employing crystal control with temperature regulated crystals and by utilizing such oscillation generators at both the sending and `receiving stations the constancy necessary for the method may be maintained. In general, it will be advisable to use a constant oscillator at the transmitter merely as controlling means for the generators which .supplyfthe .actual oscillating energy to the radiating system.

, In Figure lV a transmitting station is shown in which theoutputof a constant frequency separate control oscillator is amplified to produce two high power oscillations Vof constant and equal frequency. Each high power oscillation energizes the same antenna although obviously the oscillationsif desired, One `Yset p of the other by any appropriate well known means.v In the drawing a phase shifter is 1,794,873 i. :di n.1

shown for this purpose in the input or control of one of the high power'ampliers. The circuit arrangements of the control oscillator, amplifiers and the phase shifter are not shown in detail as my invention in this respect is not limited to any particular; apparatus of circuit arrangeinentv and for convenience legends have therefore been used.

j However, as the desired constancy` at presvadapted'to 'selectively receive tlieseroscillationsfdespitetlie vfact thatthey are or .may be of the same frequencyan'dl direction; Referring to Y Figure 2' a receiving antenna l is shown whichuinay .be tuned inthe yusual manner by means'of condenser 2 andinductance 3. The antenna'iscoupled to two similar amplifying and detecting systems A and B the corresponding 'elements ofwhich are designated bythesame reference characters.

Al portion offeach` detecting-system shown in theidrawing isithe'well known-Carson translator circuit. The translator circuits of receiver systems A and' B each'consist of two similar three' element vacuum tubes, ll,V 5, having 1 their .grids connected togetherby means of a coil-6 coupled to theaerial-coil 3. A variabler-tuning condenser 7 is connected across the coil. The middle point of the coil is connected to the filaments of the tubes through a coil 9 and avbiasingxlevice such as a battery 10 for fixing the operating potential of the: grids at a` rectifying point of the characteristic curve preferably ata negative potential. `A local constantl frequency oscillator-l1 is coupled to the 'coil 9, the connectiontocoil 9f of system B including aphaseV rotator 12a?. The plates ofthe tubes are connected. together bymeans of resistances l2 and 13 of equal value and preferably of substantially twice the order of.

`magnitude of the impedance ofthe internal plate-nlament circuits `of the valves. Between-the filaments andthe junction point of these resistances is connectedfa plate battery 14 which supplies the plate.V filament circuits of the valves.; *5 f- In orderzito utilize the Carson translator in my system I may employ to advantage a special type of detecting arrangement. This consists 4of a pair of equal resistances 15, 16 in parallel with the.` -resistancesA l2, 13, the first mentioned resistances being shunted by condensersl?, 18..A The condensei'szare of sufficiently large. value to'by-pass or yin otherwords shortcircuit frequencies of the 'order of the radio frequency -to be detected,

l Ybeing shown in-Figure 1 connected tol a were@ but not lar-ge enough to lbly-pass Sor-'short lcircuit the key or modulation frequency used in sending. Two tubes 19, 2O have their iilz'riiients.v connected tofthe junction point of the resistances 15,16 andcondensers 17, 18

through a biasing battery 21 and, coupling coil 22 to Which' anfaudio frequency oscillator 23 is coupled. `The grids of tubes 19, 20k lwhich are connected toy separated ends .of

the resistances, are ad] ustedy to a rectifying point of the characteristic curve.l Y

The plates of the tubes are .connected to v' the positive terminal of a battery 24Sthrough inductance coils 25, 26y of equalvalue Wound in the same direction. A circuit containing a telephone 27is coupled `to"inductances"25,v

26 by means of a coil 28.

In the operation of the transmitting system two'oscillations of tli-e saine' frequency will be supplied to the' radiating antenna each'ofthese being interrupted forisignal'- ing in any appropriate manner, keys 29,v 30

modulator or any suitable device'for changing the antenna radiation. The oscillations Will be maintained at a definite phase relative to each other for exam-ppl@ by coupling y.

l tivo amplifiers to the saine master oscillator and dep'hasingthe input lof one of `the amplifiers by means of the phase shifter.

In the particular system shown for the pfuri pose of illustratingthe method, the two transmitted Waves p ence of 90. The master receaving oscillator will beregulated to give substantially.dehniteV phase relation with the mastertransmitterk oscillator and by means of the phase shifter the electromotive forces of the master receiv ing oscillator Wil'l'be split to provide tivo' electromotive forces at 90o phase. 'Obviously the single oscillator and the phase rotator at the receiver and transmitter. is the equivalent I oftvvo separate sources in exact synchronisiii.v

` One VYof the auxiliary electromotive forces y is adjusted to be in phase with one of the received oscillations With respect to the potential or the grid of one of the tubes of. receiver A and it Will then be 90,O out of phase with the other receivedoscillation.. The'fauxiliary electromotive. force app-lied to receiver Bv'will i then be in phase With the received oscillation and 90 out Vof phase with the oscillation Which is in phase With the auxiliary electroinotive forces ofreceiverrA. YVith this acljustmelnt and method of operation it 'may be shown that each receiver is responsive to one of the oscillations and `unresponsive to the other. f 5

The operation of the systemmay best be shovvn by discussing some of its characteris tics. It will be noted thatwvhen neither the transmitter nor the master receiving oscillator is Working the potentials at A1 and A2 are the saine because theresistances'lQ vand .13

are equal. -No directv current potential is When the auxiliaryoscillator 11 is Working,

vbut/the transmitter is not, nol effect' isproduced.V by the'inaster receiving-oscillator on the telephones of either systeniA or B as `the fluctuations ofthe grid potentials: of tubes if and are the same andthe corresponding fluctuations ofthe plate currents produce .like

changes in the. potentials of'points A1 landlAg of system A and vpoints Bl vand B2 ofl system B. 'It'Will then be evident that under Ythese conditions noldirect current potential isiap- I plied to either detector system." Thehigh frequency fluctuations of potential Lof A1, 2.

and B1, B2 also'have no Aeffect o-iithe grids .of i

tubes 19, 2() as theyfare short circuited byy condensers17 18, andmoreover, any effects-'on` lthe grids-of tubes19,20 is balanced in the l is produced in l` plate circuits so thatno effect the telephone circuit. 1 y

vThe eifect on the receiver. vvhen the trans-`A mitter is isendiiigtwo Waves of the same fre'- quency out of phase,each.of -the're'ceived Waves being substantially in phase Withone y of the.' component yelectromotive vforces derived from the auxiliary receiver oscillator-11, is

to producea direct current potential acrossv points A1 Argief receiver VAfdue to? onefof the Waves and nodirect current/potential* across these to'- points due. tothe other Wave.- Y Simiy. `1

larlyfinfreceiver YB ar direct current potential is produced Vacros'svBj .BLy due" to said `other Wave and no directcurrentpotential across these points due to thewavetvhich produces the direct Lcurrent across Aj A2. l:It may .also `'be shown thatk the ysignal frequency and the ios y second harmoniealso exist across the 'points system." f y y Itniay be demonstrated mathematically l that .the direct current potenti all across `A`1 VA2 or B1 B2 due to the si Onalsand local source is equal to `EF :cos Where Eis the signa-1 electromotive forceelthe local electro'motive force ofthe same frequency .and qb the phase vailigle ibetweenv Ithe local electroni'otive force y AAlrAQ but. are notiitilizedV in the detecting and the ,signal 'electroinotiveforce. As the I complete demonstration oft-his characteristic involves complex mathematics a simple spe- -pciiicv illustration .of the general proposition VWill be selec'tedto show Why direct current is produced across A1`A2 and B1B2 as previously set forth. Y f

Assume tl at the electromotive force of the received signallis the same asthe electromotive-p'force applied through the auxiliary "f source. When 4theselelectromotive forces .are

insuch phase that they add in phase on'the grid of tube 4' they Will exactly oppose with lrespefztwt'o the grid of tube 5. The grid l.of

.tube 5 therefore will Vnot vary in potentiall andv therefore, the plate current of tube 5 will not vary so that there is no variation whatever in the potentialV of point A2. The grid of tube 4 however, will vary in potentialv with respect to point M from Xto` Ygfas shown in Figure 3. By operating at'the point M ofthe characteristic curve the plate current of the tube will va-ry at a radio frequency from X to Y, the average value of direct current .being Z', while as thek plate current of tube 5 does not change its current corresponds to M. As a result thedirect current potential from A3 to A1 is. greater than the direct current potential from A3 to A2 and between A1 and A2 there is a direct current 'potential proportional to Z-.M. By' similarly plotting grid potentials X14 Y1 corresponding to signal and auxiliary ,electromotive forces oic Vhalf the first illustrated value it will be seen that the average of plate current Z1,'between X1 Y1 diii'ers from M by an amount which is `substantially onefourth of ZM\". This shows graphically that the direct current potential across A1 A2 and B1 B2 varies as the product of the applied voltage, when the auxiliary electromotive force is in phase with the signal with respect to one of the grids. This can also be demonstrated mathematically as previously stated.

It will now be shown that there is no direct current across A1 A2 and Bl B2 due tothe signal which is 90 out of phase with the auxiliary electromotive force applied to the grid of tube 4.v Under these conditions Vthe potentials,V applied to the grid V4 are shown in Figure 4. lt will be noted that the resultant Vpotential is a wave Vof the vsame frequency but greater amplitude than the components and the direct current in resistance 12 is correspondingly increased. F or grid 5 Vthe signal potentialis opposite to that of grid 4 and when this is combined with the auxiliary potential the resultant is also aA wave of the same'freq iency and greater amplitude'thanV the components, but 900 Vbehind the resultant on grid 4. rlhe change of potential of the grid 5 however, is the saine as that of grid 4 so that the direct current in resistance 18 is the saine as that in resistance 12 and therefore, there is no direct current potential applied across points A1 A2 or B1 B2 for the signal which is 90o out ot phase with the auxiliary potential. The combination vof the effects of the twovsesultants gives an ampli-V fied signal frequency and a double frequency which are not ei'ective'in this arrangement, as the short circuiting condensers 17 and 18 are provided.

To show that there is some direct current between O9 Vand 90 phase relation of signalA and auxiliary potentials the potentials are plotted for a 45o phase difference betu-'eenthe auxiliary and signal potential on grid 4 (Figure 5). It will be seen that these two potentials are suhciently nearly in phases() Vpotentials'is as follows: i

that the .resultant potential on grid 4 is considerably greater than either. As a result the direct current in resistance 12islgreatly increased, theexplanation for this being similar to the previous explanation. However, in the case of the grid 5 the potentials are combined so nearly in opposite Yphasethatthe resultant is of less amplitude than either component.V

'll he direct current through `resistance B will be somewhat increased, but the increase .will be considerably less than the increase of direct. current through resistance 12. As a result there isl a direct current potential across A1 A, and-Bl B2 as well the' high frequency and'second harmonic previously mentioned. This may be shcwn mathematically to depend on the cosine ot the'phase angle between the auxiliary and signal waves. ln other words, considering the potentialon grid 4 due to the signal and the potential on grid 4 dueto the auxiliary source, direct curfre'nt across A1 A? and the'phase between the 135n (lo potential-T 180o Z0 potentialifl 225 Z0 potential=-7 270 lc potential= l0' 815". Z0 potential: -l-.7 Y3600 da potential=+ 1 lt will therefore beevident that if two signals at 909 are sent and the adjustment of the phase of an auxiliary potential is made to give ymaximum direct current at al A2 for one of two signals, there will be no direct current effect at A1 A2 tor the other signals. Even ifthe phase angle should be varied on either side by as much as 159 thev direct current across A1 A2 dueto the desired signal will only decrease from 1 to ..08 and the direct current due to the undesired vsignal will increase from 0 to .26. Y The difference inthe signal strength will, under these conditions,

enable the selection to be made. The operation of system B in the reception of the other signal and the'exclusion of thefA signal will be the same as that already described.

The discrimination o1q the receiver as-the phase relation is varied is illustrated in F igure 6 by the-curve C which is the well known ligure 8.

The curve C of Figure Gv shows that the selectivity characteristicwith phase selectivity is similar to the directional selectivity of a loop antenna. That is, interference from signals or static of the same frequency which lead or lag behind the local oscillator by 900 is entirely eliminated and it in Yphase Yor in opposite phase they are received `without diminution, but the direction of current flow isv reversed ii. the phase is reversed. At inien . i-,aeeere a circle, that is, the selectivity characteristic isV analogous to that of a vertical antenna as shown inFigure 6. The area of the ligure 8 may be shown to be equal to f where r is the received elfect when the local and received oscillations are in phase. As the area of the circle isf?. phase selectively with the arrangement shown in Figure 2 eliminates of the interference which is of the same Wave length assuming the static Vtobe uniformlydistributed as to phase. This is analogous to the benefits of directional selectivity of a loop over a vertical antenna.

Ashovvn diagrammatically in Figure 2 the u lngfja transmitter including a sonroe of'e pluk' signal'may then bevindicated-by any form of direct current responsive devices such as a telegraph sounder. InA actual operation, however, it Will be preferable to utilize the directcurrent to control another frequency source which is adapted to actuate a telephone. The advantage of this is due to the superiority of the oral reception in distinguishingV static noises from signals. To secure this result a second system vmay be used which is similar in some respects to the Carson translator. The direct current resulting from the desired signal isv impressed across the equal resistances 15 and 16 the opposite ends of Whichare'connected to the grids of tubes 19, 20, thereby causing the grids to be at'diiierent potentials While the signals are being received. This secondpair of resistances 15, 16 are used to prevent a high positive potential from'being applied to the grids of tubes 19, 20, from the battery 14. Direct current from the preceding portions of the circuit is impressed on the grids only when desired signals are being received. The conn densers 17 and 18 are of such valuev that high frequency alternating current potentials lare byfpassed therethrough but the key frequency is not. To render the signals audible the local oscillator 23 of radio frequency is used. When no'direct current is applied to the grids of tubes 19, 20, the local oscillator frequency is not heard in the telephone because the grid potentials are alike and the effects of the plate current variations on coil 28 are equal and opposite. When the grids Vof the tubes are biased to different potentials by the direct current resulting fromk the signal the variations in the plate currents in the Y valves are unequal and as a result the potentials impressed on the coil 28 by the coils 25 and 26 are unequal. The local oscillation mitted wave., lWhere. a single; wave is.y trans:

, energy appears in the output circuitsthereof frequency is therefore; heard only when a ole-` Sredfsignal received. llieoperatonof i the two detectors; of the direct current isidenl. ticatexcept that each responolstoy one of the two, sign-als, and therefore, need not be furtherfdescribed. y j I y From .the foregoing it will be. r cui dentthat certain importanti benefitsarey derived even whenI the method .islusedwith only t one transf .75 niltted it'wiil also. be advantageous to, .effect the signaling by shifting the'phase. transmitted. osc-illatiens,9.0"` Without altering thelfgrequeney or amplitude of `the fis'clla-v lonslff l v Furthelrnoreeltllonsh l here illustrated and eriloed 'e pertioelartype ofytranemittingand,receivingy system operatiHgWh @We Waves 'out/of 'plialee'ny invention S/not limited to; this number as thev method '5.5 eleozbe ntlzedjwtli more than two Waves f end with d'erent plieserelations.` f

'I'elenlr g' v., l. A. multiplex Sisnal.ne.'eyetenly compris 199' ralty of `Carrier energy components of. like constant' frequency andv different constant phase, andnleans for independent-ly keying .each of seid @au fr energy Components in accordance Wit-l1'afdlerelitone ofthe Signale '95 toloe tra1isniitted;`y and; a receiver nolndng 'a source of portoisfof looallygenerated 'energy of like frequency and proper pllesoffelatre to'eaoh oli-the received, energy oelnponents, to, discriminate therebetweennennelto Seperate,- ly combine the received carrier energy with the different portions of the locally-,generated energy to separate therlesrefl .Signa-1S, Paire of: pushpullconnectedy tubes biased alike, relativelylow frequency energy sources for Velpplyingto. the input circuits of the tubes parallel the relatively low frequency energy, Mld. means for` applying the separated lsignals t0 thetubes Wherebyrelativelylow frequency 110 and means for translating the energy S-.o en# f- Pee111-1s.

2. A multiplex signalingsystem comprise ing a transmitterincluding a source of car-r rier energy lof constant frequency and phase, means to key the carrier in accordance with a first signal, a source of carrier energy of like consta-nt frequency and Yin constant phase quadrature, meansto key this carrier in ac- ,120 cordance With a second signal, means to transmit both of said carriers, and ajreceiver in# cluding a source of locally generated energy of like frequency and in proper phase to select source of locally generated energy of like frequency and in proper phase to select thesecond signal, means to combine the received en- 130 ergy with the locally generated energy,'and translating means for the second signal, each of the ,translating means comprising pushpull connected tubesbiased alike, a relatively low frequency energy source for applying in parallel to the input circuits thereof relatively 4low frequency energy, means .for applying the selected signal to the tubes Whereby relatively 10W 'frequency energy appears in the output circuits thereof, and a device for translating the lovv frequency energy` soV appearing. 1

3. A multiplex signaling 'system comprising a transmitter including a source of 'first carrier energy y of constant frequency and phase, means to key'the first carrier in accordance With a'rst signal, a source of second carrier energy of like constant frequency and in constant phase quadrature, means to key the second carrier in accordance with a vsecond signal, and means to transmit the keyed carrier energy, and a receiver including a source of first energy of like frequency and like or opposite phase relative to the first received Y' carrier, a first pair of elect-ron emission tubes, means to apply one of said energies to the tubes invseries, means to apply the other of said energies to the 'tubes in parallel, and a translating device responsive to the dierential of the tube outputs for translating the first signal, a source of second energy of like frequency and like or opposite phase relative to the second received carrier, a second pair of electron emission tubes for combining the received energy and the second locally generated energy, meansv to apply one of said en- Y ergies to the tubes in series, means to'apply the other of said energies to the tubes in parallel, and a translating device responsive to the differential of the tube outputs for translat-V ing the second signal, each of said translating devices comprising a pair of pushpull connected l tubes biased alike, a low frequency generator applying energy in parallel to the input circuits thereof and an electromechanical translating device coupled to the output circuit thereof responsive to the relatively low frequency energy appearing therein.

ROY A. WEAGANT. 

